Piezo-electric-crystal oscillator system



Oct. 23, 1928. 1,688,713

A. HUND PIEZO ELECTRIC CRYSTAL OSCILLATOR SYSTEM Filed May 10, 1927 IN VEN TOR.

fagas 2 1941420 Patented Oct. 23, 11928.

UNITED STATES PATENT OFFICE.-

'ro WIRED Rnmo, Inc; or DELAWARE.

PIEZO-ELECTRIGCR YSTAL OSCILLATOR SYSTEM.

Application filed May 10,

My invention relates broadly to high frequency oscillators and more particularly to a piezo electric crystal control system for generating high frequency oscillations.

One of the objects of my inventlonlis to v provide a circuit arrangement for the generation of high frequency oscillations under control of a piezo electric crystal element wherein means are provided for eliminating back reactions in the circuits of an electron tube system whichmay be arranged for sustaining the oscillations.

Another object of my invention is to provide a circuit arran ement for a high frequency .oscillator wherein a piezo electric crystal element is so connected with respect to the electrodes andcircuitsiof the oscillator that sustained high frequency oscillations may be developed without interference from circuit reactions normally encountered in oscillator circuits.

Still another object of my invention is to rovide a circuit arrangement for a high requency oscillator wherein the characteristic frequency of a piezo electric c stal element may be sustained independent y of reactions which-have a tendency to develop in the circuits of the oscillator for avoiding influence of circuit oscillations upon the characteristic frequency of the piezo electric crystal elementf My invention will be more clearly under.-

6 stoo by referring to the following specification and the accompanying drawings where- Figure 1 shows diagrammatically a piezo electric crystal controlled oscillator system embodying the principles of my invention; Fig. 2 illustrates a modified construction of apparatus which may be employed in the circuit arrangement of my invention.

It can be shown theoretically as well as experimentally that a piezo-electric element vis equivalent tov a large inductance in series with a resistance and a comparatively small capacity. In a piezo electric crystal controlled electron tube oscillating system the 4 capacity of the crystal holder and that of the two tube elements (filament and grid or grid and plate) must be considered. In other words, this equivalent circuitis as. a Whole shunted by acondenser takingvinto account the various other capacity efiects. As far asoperation with radio frequencies goes the effect i'srelatively small and substantially 'cillations.

1927. Serial No. 190,303.

negligible for all practical purposes. When the beat frequency between two piezo-electric elements is utilized any error is greatly magnified in the beat frequency f -f where,

7"; and f denote the two constituent radio frequencies, It is afact that any error in any of the two frequencies. f or f is the same forthe beat frequency 'f 'f but the per,- ccntage error is I f1+f2 (f1 "f2) times as large. It is therefore essential that. any back'action from the anode branch of a] piezo electric oscillator be reduced to a mini mum. My present circuit arrangementhas been designed to avoid losses and interfer-' ence due to back actions.

Referring to the drawings reference character 1 designates an electron tube having cathode 2, grid electrode 3 and plate electrode 4. The cathode is heated by means of battery 5, the temperature being regulated through rheostat 6. The out ut circuit of the electron tube oscillator includes plate electrode 4, inductance 7 and high potential battery 8. The output of the oscillator ma be connected to any desired circuit which l have represented at 9. I have indicated the capacity 10 ositioned across the batteries 5 and 8 for sented as connected across inductance 7, which capacity may be variable ordesigned to have a selected ed value for sustaining a particular frequency. A connection is pro This cylinder is moved over the late coil until oscillations are developed. he slotted cylindrical member 16] illustrated in Fig. 2 has an advantage over the solid cylin drical member 16 in Fig. 1 by reason of the decreasing of the losses in the oscillator system. The cylindrical member 16 is moved y-passing .high frequency os- A capacity 11 has been repre-' piezo to a selected point coil 7 dependent upon the frequency to'be sustained andwuponthe value of the .fixed -orvariable capacity parallel 11 which may. beconnected across. the

capacity 11' across the winding 7 omitted oscillations may be reduced but the circuit offers such a high lmpedance wgliifisulch a at it is i cut to broad characteristic t secure the desired fundamental oscillation of 1 the piezoelectric crystal element. The bat,-

tery action fr0m. the plate circuit u onthe coil circuit is substantially negligi le and -the oscillationsfof the true frequency of the piezo electric crysta l'element are maintained. Circuit oscillations are avoided for frequencies other than that'frequency "sustained by the piezo electric crystal element My invention has been found be extremely practical and ieflicientin itsoperation, and while I have described my invention in certain of its preferred embodiments,

I desire that it that modificaelement mounted between said parallel elec trodes and a connection between one of said electrodes and said grid electrode,

, and a capacit connection between the other of. saidpa lel electrodes and a variable .po nt-onsaid inductance.

2. A'pie'zo electric crystal" controlled oscillator including: an electron tube having grid,

filament and plate electrodes, an output circuit interconnected between said plate, and

filamentelectrodes with an inductance connected therein, aiezo electric crystal eleutt-ele tr d s at, establishing c a terminals of the winding 7. With the tion frequency. corresponding connection the opposite surfaces of said piezo electricflycrystal element, a connection betweenone' of said last mentioned electrodes andsaidjgrid' electrode and a connection betweenthe other of said last mentioned elec trodes and a capacity area, said ca acity area substantially surrounding the in uctance in said output circuit. 7

t 3. A piezo electric crystal controlled oscillator including an electron tube having grid, filament and plate electrodes, an output ci rcuit interconnected between said plate and filament electrodes with an inductance connected therein, a piezo electric crystal element, je lectrt )des for establishing electrical connection with the opposite surfaces of said iezo electric crystal element, a connection tween one of said last mentioned electrodes and said grid electrode and a connection between the other of said last mentioned electrodes, and a movable cylindrical member, said cylindrical member substantially including said inductance and slidable thereover in spacial relation with respect thereto to a selected position for sustaining oscillations of a frequency corresponding to the natural frequency of said piezo electric crystal element.

4. A piezo lator including an electron tube having grid, filament and plate electrodes, an output circuit connected between said plate and filament electrodes, a coil included in said output circuit, a conductive cylindrical member slotted on one side thereof and arra ed to be moved to selected positions over said coil in capacity relation t ereto, a piezo electric crystal element, a pair of electrodes for esta lishing connection with opposite faces of said electric crystal element, a connectween one of said electrodes and said grid electrode,-and a connection between the other of said electrodes and said conductive cylindrical members for completing the capacitive connectidn through said piezo electric crystal element where y oscillations of a to the natural frequency' of-saideg ezo electric crystal element ma be sustain in said out ut circuit.

' testimony whereof I a I? si ature. u 'AUGUS D.

electric crystal controlled oscil- 

